Improvement in scroll-saws



W. H. DDBSON.

Scrnll-Saws.

Patented Feb. 24.1874.

Knventr -STATES PATENT FFICE WILLIAM II. DOBSON, OF CINOINNATI, OHIO, ASSIGNOR TO H. J. CORDES- MAN, JR., & BRO.,

OF SAME PLAGE.

Specification fofming part of Lebters Patent N0. 147,913, dated Februa.ry 24, 1874 application filed September 30, 1873.

T0 all whom z't mag; concern:

Be it known that I, WILLIAM H. DOBSON, of (Jincinnati, Hamilton eounty, State of Ohio, hzwe invented a eertain new and usfu1 Improvemen in Scro1l-Szuvs, of whieh the following is Eh specification:

My invention reIa-tes to the dass of devices designed t0 strain scroll-saws a11d oher reciprocating instrumentalities, while nndera reciprocating motion; and my invention consists 0f a stra.ining device composed essentially of four elements, t0 Wit: A ditferentiai traversingpul- 1ey, a strap 110 connect thesaw With the large dimneterof the pulley, a. spring for straining, zu1d astrap 01 straps t0 oonuect the strainingspring With the small arts of the pulley, the object being t0 ha.ve bat litt1e motion 0f the spring Wit-h a great extent 0f reciproeating 1110ti011 0f the saw, aa1d bat little friction 0f the movin-g parts.

Figure l is a perspetive view of 1ny st-minin g device complete f01 attacinnent t0 a scrollszuv 0r other instrnmentality requiring strainingwhile in motion. Fig. 2 is a vertical section of reciprooating scroll-saw to which my straining device is app1ied.

The' scroll-saw 150 which my straining devioe is applied in Fig. 2 is 0f the ordinnry description, A being the tab1e, B the saw, O the drivin g-pitman, und D the clifivingshafb. The coustruction 0f my straining device is as follows: A frznne, E, is provided, bemveen the upper end 0f which and the projetion e a rod, F, is snpported, surronnded by the straining-spring G, which rests upon an a.dj ustable mit, H, upon said rod. A yoke, I, is fitted 130 move freely up and down the rod F, und ans it embraces 01 rests upon 13110 spring i is adapted t0 compress the lntter between the y0ke itse1f and the nut H. The yoke is hooked or otherwise attached to the stra.ps J, which are secured 150 the small diameter ends k 0f a difierential pulley, K, in the manner showxn The central ortion k of the diflerential pulley is embrzwed by a sfirap, L, which is secnred t0 1't by pin Z, 0ne end of the strap being secured 130 the. frame E ab e, and the other end adapted for attaehment 130 the saw 01 other reciprocating instrumentalitv, by means 0f the 1100k M, 0r otherwise.

In the operation of the machine, when the sa.w is descending, the difierential pulley, while revolving, deseends a1: half the rate 0f speed 0f the saw, a.nd this descent 0f the pulley is a.gzminst the acion of the stmining spring, as owing 00 the sma1l diameter of the ends for the straps J they cannot be unwound as rapidly as 1:11e pu1ley descends. The spring is, therefore, necessarily compressed in the descent of the sa.w. In the return-stroke the saw is earried up by the force of the spring, owing 150 the differenee 0f the levera.ge between the radius 0f the larger part 0f the differential pulley zmd the sm aller part. T0 prevent displacement 0f the differential pulley while in motion, a bed or track, N, is provided, upon which the stra.p L is laid zus the pulley ascends, and the strzmps J are slightly inclined so as to cause the pulley K with its stra.p L t0 hug the track 0r bec1 N, and thus remain in proper 1ine.

It Will be seen that owing to ehe traversing eharacter 0f the pu'lley K, and the prculiarity 0f its connection with t-he spring G, that thc motion of the spring is bat slight, El/lld consequently the strain impa.rted by it t0 the saw is mzninta.ined nearly uniform during the reciprooa.ting movement: 0f' tl1e. saw, or other reciprocating instrumentality.

I1; is obvious that this stra.ining device is applica.ble t0 mortising-machines, reciprocating tenoning-maehines, and ot-her analogous nse, in Which n reoiprocating instrumenta.ility is employed, which requires straining so produee a reverse aetion.

This device ma.y be arranged for vertical action, horizontal aetion, 0r inclined, and the spring may be connected With the straps in mzu1y other ways from that shown withont departing fr0n1 the characterisnic features 0f my invention.

For a seroll-saw, 01 other analogous use, the straining device herein described, consisting 0f differential traversing-pulley K, connectingstraps J L, and spring G, conneoted and operating substantially in the manner and f0r t]ie purpose spem'fied.

In testimony 0f which invention I hereunto sei: my band.

W. H. DOIBSON.

Witnesses:

FRANK MILL\VARD, J. L. VARTMANN. 

